Investigations into the determinants of hyperactivity have focused primarily on biochemical factors to the neglect of evidence suggesting the situational dependence of the disorder. The research proposed here will involve a systematic investigation of environmental and task stimulation precipants of hyperactive behavior and performance problems. Earlier work by the applicant suggests that environmental and task stimulation can directly affect performance and activity of hyperactive children. Certain moderating variables likely to be important in investigating these effects have been identified from patterns and inconsistencies in reported findings: (1) the nature of the task (e.g., learning versus practice tasks, task modality input), and (2) inherent task requirements that may provide changes in level of stimulation (e.g., scanning requirements, length of task exposure, temporal placement and locus of added stimulation). Population factors (hyperactive learning disabled, hyperactive normal, nonhyperactive learning disabled and nonhyperactive normal children) will be examined in order to determine whether the assumed clinically defined severity of the referred children is related to experimentally assessed differences among groups. This systematic study of the interaction of task, environment, and child variables is theoretically based and has been developed broadly to include multidisciplinary treatment and diagnostic techniques.